Q: Does Liquor go bad?
A: Well, it depends. Liquor is a very broad category, covering hundreds of types of alcohol. You can break them into two basic groups: Spirits and Liqueurs. Spirits are the distilled products we all know, Brandy, Vodka, Gin, Rum, Tequila, and Whiskey, as well as other more exotic distillates. Liqueurs, also known as cordials, are a distilled spirit that is sweetened and has other flavors, oils and extracts added to it. These can be a recipe of herbs, cream or eggs, coffee or fruits of various types.
There are three things that make both go bad: Light, Heat and Oxygen. Daylight is the most damaging, and long exposure to it can change the color of a liquor, and that usually damages some of the flavors as well. Prolonged exposure to heat, or exposure to intense heat, breaks down the organic molecules in them and that destroys the flavor. Oxygen exposure can over time also affect a liquor’s flavor, and in some cases cause it to actually spoil. You will be able to tell if it has spoiled by a bad smell, taste or a change in texture.
Spirits are much hardier than liqueurs. An unopened bottle of spirits stored away from light and heat can last for a very long time, 10 years or more! And even one that is opened and partially consumed, resulting in more exposure to oxygen, will only have a moderate flavor loss, though over time it will start to evaporate, too! Opened spirits will see the flavor loss within a year or two, and eventually cease to taste of much at all. But they will not get moldy, coagulate or become “toxic”.
Liqueurs are a little more complicated. The main problem is with cream or egg based liqueurs. These are very sensitive to heat and oxidation and they will curdle. This means once you open them, the clock is ticking! You really want to consume these liqueurs within the year. As an example, Bailey’s Irish Crème recommends drinking their product within 2 years of its manufacture, opened or not. The other problem with liqueurs is the sugar content. Because liqueurs have more sugar in them than liquors, they do feel the effects of oxidation and heat more profoundly. They start losing flavor if not stored well, but will not curdle like a cream will.